A noun for “ox” appearing in the Qenya Lexicon of the 1910s with variants yakko and yako, derived from the early root ᴱ√Ẏak “a head of cattle” (QL/105). In the contemporaneous Poetic and Mythological Words of Eldarissa Tolkien had yakk- “ox” (PME/105). In Early Qenya Word-lists of the 1920s, the word for “ox” was also yakko (PE16/132).
Early Quenya
taruku
noun. ox
tarukko
noun. bull, ox
tarunko
noun. bull
yak(k)o
noun. ox
A noun in the Qenya Lexicon of the 1910s glossed “bull” with variants tarukko and tarunko, an elaboration of ᴱQ. taru “horn” (QL/89). In the contemporaneous Gnomish Lexicon, taruku- was given as the Qenya cognate of G. tarog “ox” (GL/69).